A review of theoretical concepts of the ways of producing 129Xe nuclei hyperpolarized in magnetic moment by optical pumping of alkali atoms with their subsequent collisional spin exchange (SEOP) with noble gas isotopes is given. For completeness of presentation, a brief review of other known methods for the polarization of nuclear magnetic moments is also presented. In describing the most important process in SEOP for the transfer of spin polarization from electrons to nuclei, a simple quantum mechanical model of this process is used.

A new method of determining the dimensions and shapes of polymer molecules in solutions is proposed and verified in experiments. The method is based on the measurements of the relaxation of the transverse magnetization intensity of nuclei. It is established that the decaying signal of the spin echo from elongated molecules contains two terms exponentially decaying with time, which correspond to two diffusion coefficients differing by a factor of about two. The signal from molecules with a near-spherical shape contain only one exponent.

Рассмотрено взаимодействие двух медленных атомов, адсорбированных на поверхности. Показано, что, аналогично ефимовским состояниям трёх частиц, при любом знаке длины рассеяния у этой системы имеется связанное состояние.

The interaction between two slow atoms adsorbed on the surface is considered. It is shown that, similar to Efimov states of three particles, this system has a bound state at any sign of the scattering length.

A model water-filled porous medium is investigated using NMR techniques, and the results of these measurements are interpreted theoretically. A rigorous theoretical description of the near-surface layer, qualitatively introduced when interpreting the NMR data for porous materials, is formulated. Our results indicate that the thickness of the near-surface layer exceeds that quoted in the literature by several orders of magnitude. This result allows to obtain valuable information about the processes at the liquid-solid interface.

The conditions of suppressing the collective slowing-down of an ionic beam on electrons, which is caused by the excitation of electron plasma oscillations (beam instability) by ions, are found. In contrast to available explicit and implicit indications, a large spread of the energies only in an ionic beam is insufficient for this suppression. The acceleration of ions is shown to become stable when a sufficiently large spread of the electron velocities is simultaneously present. The beam instability of ions is suppressed by the Landau damping of the ion-excited plasma waves at electrons. The results obtained are used to analyze the possibility of ion acceleration by collapsed cylindrical plasma liners.

The conditions for the absence of Alfven ion-cyclotron instability during the creation and subsequent acceleration of ion rings by compressed cylindrical plasma liners are established

We have established the conditions for the absence of Alfvén ion-cyclotron instability in the formation and subsequent acceleration of ion rings by collapsing cylindrical plasma liners.

Carbonylation of o -dibromobenzene and its derivatives in the presence of palladium phosphine complexes with NaOAc or Et 3 N additive leads to the formation of phthalates in high yield under mild conditions. Correlation NMR spectroscopy data and semiempirical calculations have shown that the reactivity of the C–Br bond is enhanced with the increase in the positive charge at the carbon atom, in line with the results of kinetic experiments.

The relaxation of the proton magnetization of water and hydrocarbons in a model medium of glass beads and quartz sand is studied by the NMR method. The spectrum of relaxation times of fluids is one-component in the model environment and three-component in quartz sand. The surface relaxivities measured in the model medium are used to determine the pore size distribution in quartz sand. Estimates of the specific surface area of sand based on the relaxation data are consistent with the values measured by the sorption method. The EPR method is used to determine the chemical nature of the active paramagnetic centers responsible for the surface relaxation of the proton magnetization. Differences in the relaxation behavior of aqueous and hydrocarbon fluids are interpreted within the framework of a simple model of surface relaxation.

Methane-intercalated fullerite (CH4)0.56C60 was obtained by low-temperature precipitation from solution. Methane transition from the gas phase to the octahedral void of fullerite is accompanied by a bathochromic shift of normal vibrational frequencies (by 19 and 8 cm−1 for ν3 and ν4, respectively). The methane 13C signal in the proton decoupling 13C NMR spectrum is observed as a singlet at δ−0.42. According to quantum chemical calculations using density functional theory, location of methane in the octahedral void of fullerite (C60)6 leads to a decrease in the total energy of fullerite by 4 kcal mol−1.

The methods of solid-state high-resolution NMR have been applied to investigate samples of fullerite C-60, doped with molecular oxygen. It was found that in the case of well-crystallized (O-2)(0.44)C-60 sample the temperature dependence of the relative chemical shift of the satellite peaks reveals jump nearly the orientational phase transition temperature. At temperatures above the phase transition, the shift due to the redistribution of electron density was similar to 0.1 ppm, which corresponds to the transfer of 0.05 electron from O-2 molecule to the fullerene molecule.

Based on perfluorinated polymers MF-4SK and F-4KF bilayer composite ion-exchange membranes are studied by using the magic-angle-rotation NMR, electrochemical impedance spectroscopy, scanning electron microscopy, and electron-probe microanalysis. It is shown that the contact of the polymers includes an interlayer, approximately 5 μm thick. The NMR data point to slow water-molecules-exchange between hydrate-complexes of sulfo- and carboxyl-groups.

Oxidized fullerite was obtained by heating a fullerite sample intercalated with oxygen, (O2)0.44C60, up to 300 degrees C. Orientational phase transitions in the oxidized fullerite are studied using differential scanning calorimetry (DSC) and have been found to possess a specific enthalpy whose value is lower by 25% than in the initial (O2)0.44C60 sample. In order to find possible reasons for hindrance to the buckyball rotations, we performed optimizations of defect buckyball fullerenes C60-n with different distributions of vacancies along with the dimers C60-n-C60-n and C60-C60-n for n = 1-4 using density functional theory with generalized gradient approximation. We found that the dimerization energy ranges from 1.07 eV (C58-C58) to 6.56 eV (C56-C56) and from 1.81 eV (C60-C58) to 4.29 eV (C60-C56), respectively. The formation of such dimers, which could in addition interact with defect buckyball cages and form larger aggregates, is to be related to the lowering of the orientational transition enthalpy.

The mobility of the polymer matrix and the structure of the hydration complex in the acid forms of perfluorinated ion exchange membranes MF-4SK and F-4KF depending on moisture content were studied by 1H, 13C, and 19F solid-state high-resolution NMR. A correlation between an increase in mobility of separate polymer matrix segments under hydration conditions and their hydrophilic properties was observed. Carboxyl groups in F-4KF membranes were shown to exist as dimers C(OOH)2C, and the main hydrated complex form in MF-4SK membrane under low moisture content conditions was the hydroxonium ion H5O 2 + .

A (O2) x C60 sample with a high content of oxygen (x ≥ 0.4) and free of technological solvent impurities was obtained by precipitation from solution. For the first time, the results of the determination of the x coefficients using 13C NMR and elemental analysis were compared. It was shown by Raman spectroscopy, mass spectrometry, and NMR that the inclusion of oxygen into fullerite was accompanied by a decrease in the frequency of O=O stretching vibrations by no less than 12 cm−1 compared with gaseous O2. Nevertheless, oxygen exists in the molecular form in (O2)0.4C60 and is released in the form of O2 as the sample is heated to 373 K. The number of oxygen molecules occupying octahedral pores closets to the fullerene molecule takes on all the possible values, from 0 to 6. At room temperature, the (O2) x C60 sample lost oxygen much more slowly than similar products prepared by diffusion saturation of pure fullerite with oxygen.